In these days, researches and developments for power saving from the perspective of Green IT (Information Technology) are conducted actively.
In Patent Document 1, there is a proposal on transmission power controlling method at one or more radio base stations arranged in each of a plurality of service areas of a mobile communication system in which radio communication is carried out between the radio base station and a mobile station. The mobile communication system is presupposed to be a PHS (Personal Handy-phone System) which is a simplified mobile phone system that uses a micro-cell. The radio base station is configured to receive a signal sent from the other radio base station(s) to control the transmission power at its own station based on the relationship between the information concerning the state of communication in the other radio base station(s) as derived from the received signal and the power of the signal received from the other radio base station(s).
More specifically, the radio base station monitors                traffic status at neighboring radio base stations, and        received power from neighboring radio base stations.        
The radio base station performs control to decrease the transmission power if the monitored result indicates that the received power at its own radio base station from another base station (neighboring radio base station) exceeds a predetermined required threshold value and such another radio base station is in a low traffic situation.
If the radio base station of interest decreases its transmission power, but the received power from the other radio base station exceeds the required threshold value, a mobile terminal engaged in communication with the radio base station is able to hand over to the other radio base station. Hence, call disconnection is not happened, thus presenting no problem.
Thus, with the transmission power controlling method for the radio base station of Patent Document 1, each radio base station is able to autonomously control the stop and start of transmission in keeping with each surrounding status. It is thus possible with the transmission power controlling method for the radio base station of Patent Document 1 to flexibly deal with considering the traffic states to achieve power saving.
On the other hand, from the perspective of reducing the operation cost (OPEX), researches and developments on SON (Self Organizing Network) in a radio communication system, are actively carried out.
SON has the following functions:                self-configuration;        self-optimization;        self-healing; and so forth.        
Techniques that will accomplish respective different objectives (Non-Patent Documents 1 and 2) are under study.
In Non-Patent Document 1, optimization of the radio parameter is introduced as one of the SON techniques. It is intended to achieve different objectives such as                maximizing throughput characteristic;        minimizing delay;        maximizing network capacity; and        maximizing coverage.        
Examples of radio parameters include                transmission power of a base station;        antenna tilt angle of a base station;        neighbor cell information; and        handover parameter.        
One or more of these radio parameters is changed where appropriate in order to achieve the above mentioned objectives.
In Patent Document 2, there is disclosed a configuration in which, in case a radio base station (6f) is newly installed, the radio base station (6f) sends information indicating a status of the own station (6f) to a neighboring base station (6e) that most strongly received a perch channel from another radio base station. The information indicating the status of the own station (6f) includes a use frequency information or a location information, for example, and is sent over a channel that may be received by another radio base station, such as over a common control channel. The neighboring base station (6e) receives this information to take out therefrom the information that represents the status of the radio base station (6f) to notify to the other neighboring base stations (6a to 6d) the information regarding the newly installed radio base station (6f) via a base station control station (3e). These neighboring base stations (6a to 6d) autonomously update databases of neighboring zone information that they hold, i.e., neighboring zone information needed for a mobile station to switch a channel, by way of updating a neighboring zone table by addition of the radio base station 6f. The neighboring base stations broadcast updated neighboring zone information to each mobile station over a multicast channel which is a downlink common control channel. In this manner, each mobile station is able to recognize the presence of the radio base station (6f) to wait in a radio zone of the radio base station (6f) or to switch to a channel for the radio base station (6f). In Patent Document 2, in case a base station is newly installed or removed (after operation), it sends a notification regarding new installation or removal to the neighboring base station(s) over a radio path to allow addition to or removal from the neighboring zone tables.